The Public Interest Law Center of Philadelphia said the groups, including the American Civil Liberties Union, would appeal the decision to the state Supreme Court with a request for fast-track consideration "to ensure that the over 1 million Pennsylvanians who do not have the ID required by the law ... are not deprived of their constitutional right to help shape their future."

A Philadelphia Inquirer analysis suggested authorities do not know specifically how many voters may be affected by the new law.

Law center Executive Director Jennifer Clarke said the Supreme Court, the state's court of last resort, could hear arguments and announce its decision within a month.

The center and other aligned groups have argued the law, similar to laws recently passed in 10 other states that require a special form of voter ID, was a Republican attempt to repress voting by people who are less privileged and who opinion polls indicate tend to vote for Democrats.

The law's backers said it preserves the integrity of the electoral process.

"I think we're on track to make sure that we re-instill integrity in our election process," said state Rep. Daryl Metcalfe, a western Pennsylvania Republican who championed the photo-ID requirement.

Democratic state Sen. Daylin Leach, who proposed a repeal of the law after state election officials initially produced a list of 758,000 Pennsylvania voters without the so-called PennDot identification, said, "This is going to be a catastrophe if it's upheld by the Supreme Court."

Commonwealth Court of Pennsylvania Judge Robert E. Simpson Jr. said in his ruling Wednesday partisan politics might have been a motive behind the law and the ID requirement might indeed cause difficulties for tens of thousands of voters Nov. 6.

But these reasons were not sufficient to render the law unconstitutional, he ruled, citing judgments from state and federal courts giving legislatures leeway to regulate voting unless restrictions are imposed in a plainly biased or burdensome way.

"The photo ID requirement of Act 18 is a reasonable, non-discriminatory, non-severe burden when viewed in the broader context of the widespread use of photo ID in daily life," wrote Simpson, a Republican, in his intermediate appellate court ruling.

"The commonwealth's asserted interest in protecting public confidence in elections is a relevant and legitimate state interest sufficiently weighty to justify the burden," his opinion said.

The lawsuit Simpson's ruling addressed sought a preliminary injunction of the law, which is to take effect next month. It was filed on behalf of 10 Pennsylvanians facing difficulties obtaining the proper ID.

The lead plaintiff, Viviette Applewhite, 93, is a black Philadelphia resident who lost her only form of identification when her purse was stolen.

Pennsylvania acknowledged in the case it had no evidence of voter fraud at polling stations.

President Barack Obama's re-election campaign spokeswoman Jen Psaki told reporters Wednesday the campaign would work "to ensure all eligible voters have the information they need to get to the polls in November and exercise their right to vote."

"Since the passage of the law our campaign has included information on the new provisions in volunteer trainings, information resources, online, and in voter registration and education activities, and we will continue to do so," Psaki said. "Now more than ever it is important that the commonwealth follow through on its plan to make available free IDs to any voter who may need them. Regardless of party affiliation, we support ensuring any voter eligible to cast a ballot has the right to do so."

Psaki also talked about a court challenge in Ohio to a new policy implemented by Republican state elections officials to do away with some early-voting hours for most voters while retaining them for military personnel.

"We made the strong case this morning that we believe in restoring equal and fair access to early voting and removing arbitrary obstacles to voting," she said.

Psaki said the case was about "restoring in-person early voting on the three days prior to Election Day for all eligible Ohio voters, including military and overseas voters."

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